Energy use analysis in commercial buildings has been performed for many years by a number of software simulation tools which seek to predict the comfort levels of buildings while estimating the energy use. The underlying principles of these tools concentrate on the building itself and the desire to keep that building at a particular level of warmth and/or humidity.
Occupant comfort is assumed to be serviced based on generalized set of parameters and tables used by designers in specifying the building and plant within it. It has been shown over several years that the predictive strength of these tools is not strong when comparing the design estimates of energy use with the reality, post-occupation. It is important that simple tools are developed to help operations and facilities staff to more easily measure, monitor and manage energy usage in their buildings. This method has been developed in an effort to facilitate the determination of an important and unique whole-building thermal property called the natural thermal lag. The method seeks to only use data which is readily available in buildings today.